title: Quantum information storage using tunable flux qubits.
abstract: We present details and results for a superconducting quantum bit (qubit) design in which a tunable flux qubit is coupled strongly to a transmission line. Quantum information storage in the transmission line is demonstrated with a dephasing time of T(2)∼ 2.5 µs. However, energy lifetimes of the qubit are found to be short (∼ 10 ns) and not consistent with predictions. Several design and material changes do not affect qubit coherence times. In order to determine the cause of these short coherence times, we fabricated standard flux qubits based on a design which was previously successfully used by others. Initial results show significantly improved coherence times, possibly implicating losses associated with the large size of our qubit.
authors.affiliation: IBM Watson Research Center, Yorktown Heights, NY 10598, USA. msteffe@us.ibm.com
authors.forename: Matthias
authors.initials: M
authors.lastname: Steffen
authors.forename: Frederico
authors.initials: F
authors.lastname: Brito
authors.forename: David
authors.initials: D
authors.lastname: DiVincenzo
authors.forename: Matthew
authors.initials: M
authors.lastname: Farinelli
authors.forename: George
authors.initials: G
authors.lastname: Keefe
authors.forename: Mark
authors.initials: M
authors.lastname: Ketchen
authors.forename: Shwetank
authors.initials: S
authors.lastname: Kumar
authors.forename: Frank
authors.initials: F
authors.lastname: Milliken
authors.forename: Mary Beth
authors.initials: MB
authors.lastname: Rothwell
authors.forename: Jim
authors.initials: J
authors.lastname: Rozen
authors.forename: Roger H
authors.initials: RH
authors.lastname: Koch